After working with Django professionally since more than 2 years, I would love to make this my first contribution. If I provided a patch (with tests and documentation), would there be any chance that it will be merged?

I actually only replaced one line of Django code with a few more lines. The change is quite trivial.
The original code was not yet covered by the test suite, so I added new tests and increased the test coverage for utils/formats.py.
I also updated to docs.